A method for checking the consistency of the field strength of a perfluoroisobutyronitrile mixed gas surface discharge

Abstract

The application discloses a perfluoroisobutyronitrile mixed gas surface discharge field strength consistency checking method, and belongs to the technical field of advanced electrical equipment. The method firstly constructs a surface discharge field strength reference data set under different mixed proportions, gas pressures and insulating sample heights, then carries out a standardized surface discharge test on a plate-plate electrode structure, obtains a discharge field strength test value and fits a correlation formula; pressure checking coefficients, size effect checking coefficients and proportion checking coefficients are introduced for quantitative checking, any checking condition is met to determine that the data are consistent, unqualified data are repeatedly tested and modified, and qualified data are iteratively expanded to expand the reference data set. The application can effectively unify test data under different working conditions, reduce test errors, accurately obtain the surface discharge field strength, improve the safety and accuracy of surface insulation design of the environmental protection gas insulated equipment, is simple and easy to implement, and has remarkable engineering application value.

Description

Technical Field

[0001] This invention relates to the field of advanced electrical equipment technology, and in particular to a method for verifying the consistency of surface discharge field strength of a perfluoroisobutyronitrile mixed gas. Background Technology

[0002] Perfluoroisobutyronitrile (C4F7N), as an environmentally friendly insulating gas, is widely regarded as a potential alternative to sulfur hexafluoride (SF6) due to its low global warming potential (GWP) and excellent insulation properties. In practical gas-insulated equipment, insulating gases often form composite insulation structures with solid insulating materials (such as epoxy resin, polytetrafluoroethylene, etc.), and surface discharge is one of the most common insulation failure modes inside such equipment.

[0003] Currently, research on the insulation properties of C4F7N mixed gases mainly focuses on the gas gap breakdown field strength, while accurate methods for obtaining and verifying its surface discharge field strength are still immature. Existing methods typically use empirical formulas for the breakdown field strength under a uniform electric field, and then take a certain insulation margin, ignoring the influence of actual electrode structure, gas pressure, mixing ratio, and surface interface effects, leading to excessive design margins or insulation risks. In addition, due to the large dispersion of surface discharge, different researchers use different experimental conditions (such as gas pressure, surface distance, mixing ratio, etc.), resulting in large differences in experimental results. There is a lack of a systematic and repeatable method for verifying experimental consistency, making it difficult to effectively verify the surface discharge field strength under different operating conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a method for verifying the consistency of surface discharge field strength of perfluoroisobutyronitrile mixed gas, which solves the problem of poor consistency of surface discharge field strength data of C4F7N mixed gas in the prior art, and improves the safety and accuracy of surface insulation design.

[0005] To achieve the above objectives, the present invention provides a method for verifying the consistency of surface discharge field strength of a perfluoroisobutyronitrile mixed gas, comprising the following steps: S1. Construct a reference dataset of surface discharge field strength of perfluoroisobutyronitrile mixed insulating gas under different test conditions based on publicly available data. The test conditions include the mixing ratio, gas pressure, and height of the insulating specimen of the perfluoroisobutyronitrile mixed insulating gas. S2. Conduct surface discharge tests to obtain the surface discharge field strength of perfluoroisobutyronitrile mixed insulating gas under different insulation test heights and different gas pressures. S3, Introduce pressure verification coefficient K y Size effect check coefficient K c and proportional verification coefficient K bThe discharge field strength test values ​​obtained in S2 are then checked for pressure, size effect, and proportion. If the corresponding check requirements are met, the discharge field strength test results of S2 are deemed to be consistent. If the check requirements are not met, S2 is repeated until the test results meet the check requirements. S4. The test results that meet the verification requirements are incorporated into the reference dataset of S1 as reference data for subsequent test data consistency verification.

[0006] Preferably, in S1, the surface discharge field strength of the perfluoroisobutyronitrile mixed insulating gas is the ratio of the discharge voltage of the cylindrical insulating specimen to the height of the specimen. E ref The perfluoroisobutyronitrile mixed insulating gas is formed by mixing perfluoroisobutyronitrile with one or two of the following gases: N2, CO2, and O2, in a preset ratio.

[0007] Preferably, in S2, the surface discharge test specifically includes the following: S21. Construct a surface discharge test model, which includes a high-voltage electrode, a grounding electrode, and a solid insulating test specimen placed between the two electrodes. The electrodes adopt a plate-to-plate structure to form a clear surface path. S22. Place the surface discharge test model in a sealed test container with controllable gas pressure, and fill it with a pre-proportioned perfluoroisobutyronitrile mixed insulating gas to the set pressure. S23. Apply a standard lightning impulse voltage and use the step-up / step-down method to obtain the surface discharge voltage. U d That is, the voltage at which the probability of surface flashover is 50%; S24. Based on the height of the insulation test specimen d Discharge voltage U d Calculate the surface discharge field strength E exp ; S25. Within a certain range, adjust the air pressure to different values, repeat steps S23-S24, obtain the discharge voltage and discharge field strength under different air pressures, and fit the formula for the change of discharge field strength with air pressure. E exp1 = f 1( p ); S26. Adjust the mixing ratio of the perfluoroisobutyronitrile mixed insulating gas, repeat steps S23-S24, obtain the discharge voltage and discharge field strength under different mixing ratios, and fit the formula for the change of discharge field strength with mixing ratio. E exp2 = f 2( k ); S27. Adjust the height of the insulating test specimen, repeat steps S23-S24, obtain the discharge voltage and discharge field strength at different specimen heights, and fit the formula for the change of discharge field strength with specimen height. E exp3 = f 3( k ).

[0008] Preferably, the pressure verification coefficient K y This refers to the ratio of the fitted or extrapolated value of the test discharge field strength to the discharge field strength of the reference dataset when the test conditions and the same insulating specimen height, the same mixing ratio, and different air pressures are the same; the pressure verification requirement is 1- d y <K y <1+ d y , d y Allowable margin for stress verification; The size effect check coefficient K c This represents the ratio of the fitted or extrapolated value of the test discharge field strength to the discharge field strength of the reference dataset when the test conditions and reference dataset have the same air pressure, the same mixing ratio, and different insulation specimen heights; the size effect verification requirement is 1- d c <K c <1+ d c , d c Check the allowable margin for size effect; The proportional verification coefficient K b This is the ratio of the fitted or extrapolated value of the test discharge field strength to the discharge field strength of the reference dataset when the test conditions and the reference dataset have the same air pressure, the same insulating specimen height, but different mixing ratios; the ratio verification requirement is 1- d b <K b <1+ d b , d b This is for the allowable margin of proportional verification.

[0009] Preferably, in S3, the verification requirement is to meet any one of the verification conditions of pressure verification, size effect verification, and proportional verification.

[0010] Therefore, this invention employs the aforementioned method for verifying the consistency of surface discharge field strength in a perfluoroisobutyronitrile (PFOS) mixed gas. This method effectively addresses the issues of poor data consistency and lack of systematic verification methods for surface discharge field strength in PFOS mixed insulating gases. Quantitative verification is achieved through pressure, size effect, and proportional three-dimensional coefficients, unifying test data under different operating conditions. Standardized test procedures reduce test errors, accurately obtain the true surface discharge field strength, and improve the safety and accuracy of surface insulation design. Verified data can be iteratively expanded to include a reference dataset. The method is simple to implement and adaptable to multiple scenarios.

[0011] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0012] Figure 1 This is a front view of the surface discharge test model structure of the present invention; Figure 2 This is a top view of the surface discharge test model structure of the present invention; Figure 3 This is the pressure verification result of the surface discharge test data of the C4F7N / CO2 mixed gas of this invention; Figure 4 This is the flowchart of the surface discharge consistency verification method in C4F7N mixed gas of the present invention.

[0013] Figure Labels 1. Epoxy resin supported circular plate; 2. High voltage electrode; 3. Epoxy resin supported column; 4. Cylindrical insulating test specimen; 5. Grounding electrode. Detailed Implementation

[0014] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0016] Example 1 The following is combined Figure 1~4 The method for verifying the consistency of surface discharge field strength of the perfluoroisobutyronitrile mixed gas described in this invention is further described in detail. This embodiment uses a C4F7N / CO2 mixed insulating gas as the research object, and fully illustrates the implementation process of the verification method. Those skilled in the art can refer to this embodiment to replace the mixed gas components and adjust the test parameters to complete the verification under other operating conditions. The specific steps are as follows: S1. Construct a reference dataset for surface discharge field strength.

[0017] By researching and compiling data from publicly available academic literature and experimental reports, a reference dataset of surface discharge field strength for C4F7N / CO2 mixed gas is constructed. In this embodiment, for example... Figure 3 As shown, the details are as follows: Test conditions: Mixing ratio 5% C4F7N + 95% CO2, height of cylindrical insulating specimen 10mm, air pressure 0.1MPa~0.3MPa; Reference field strength E ref Based on the discharge voltage / sample height calculation, 0.1 MPa is 52 kV·cm. -1 0.2MPa is 96kV·cm -1 0.3MPa is 126kV·cm -1 .

[0018] S2. Conduct surface discharge tests.

[0019] S21. Construct a surface discharge test model. The model includes a high-voltage electrode, a grounding electrode, and a solid insulating specimen placed between the two electrodes. The electrodes adopt a plate-to-plate structure to form a clear surface path. In this embodiment, the model includes an epoxy resin supported circular plate 1, a high-voltage electrode 2, an epoxy resin supported pillar 3, a cylindrical insulating specimen 4, and a grounding electrode 5 (see...). Figure 1 , Figure 2 The height of the insulating test specimen is fixed at 10mm.

[0020] S22. Sealed inflation: Place the surface discharge test model in a sealed test container with controllable pressure, and fill it with a C4F7N / CO2 mixed gas. Set the test pressure range to 0.1MPa~0.8MPa.

[0021] S23. Obtain the discharge voltage: Apply a standard lightning impulse voltage of 1.2 / 50μs and use the rise-fall method to obtain the discharge voltage when the probability of surface flashover is 50%. U d .

[0022] S24. Calculate the test field strength: based on the height of the insulating specimen. d Discharge voltage U dCalculate the surface discharge field strength E exp .

[0023] S25. Fitting the pressure correlation formula: Adjust the pressure to 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, and 0.8MPa, repeat S23~S24, obtain the discharge voltage and discharge field strength under different pressures, and fit the formula for the discharge field strength as a function of pressure. E exp1 = f 1( p ) = 302.58 × p 0.6997 .

[0024] S3. Conduct consistency verification.

[0025] Introducing a pressure check factor K y The discharge field strength test values ​​obtained in S2 are subjected to pressure verification. If the corresponding verification requirements are met, the discharge field strength test results of S2 are deemed consistent. If the verification requirements are not met, S2 is repeated until the test results meet the verification requirements. The pressure verification coefficient K... y This refers to the ratio of the fitted or extrapolated value of the test discharge field strength to the discharge field strength of the reference dataset when the test conditions and the same insulating specimen height, the same mixing ratio, and different air pressures are the same; the pressure verification requirement is 1- d y <K y <1+ d y , d y Allow for margin in stress verification.

[0026] In this embodiment, a pressure verification allowable margin is set. d y =5%, verification criteria: 0.95 < K y <1.05; Calculate the pressure check factor K y Specifically as follows: 0.1MPa: K y =60 / 52=1.16, which is outside the range of 0.95~1.05, so the verification fails; 0.2MPa: K y =98 / 96=1.02, within the allowable range, the verification passed; 0.3MPa: K y =130 / 126=1.03, within the allowable range, the verification passed; Table 1. Pressure Verification Results of Surface Discharge Field Strength Test Values ​​for C4F7N / CO2 Mixed Gas

[0027] Repeat step S2 to conduct the surface discharge test again at 0.1 MPa pressure, and the discharge field strength was measured to be 54 kV·cm. -1 Recalculate K y =54 / 52=1.04, satisfying 0.95<K y <1.05, verification passed.

[0028] S4. Update the reference dataset.

[0029] Test data that passed the calibration at 0.1MPa, 0.2MPa, 0.3MPa, and 0.4MPa~0.8MPa were incorporated into the reference dataset of S1 to form an expanded standard reference library, which can be used for consistency verification of subsequent tests of the same type.

[0030] This embodiment completes the consistency verification of test data through pressure verification. If size effect verification or proportional verification is required, it is only necessary to fix the corresponding test parameters, replace the verification coefficients, and execute according to the same logic. The test results are deemed valid if any one of the verification conditions is met.

[0031] To perform size effect verification, adjust the height of the insulating specimen and repeat steps S23-S24 to obtain the discharge voltage and discharge field strength at different specimen heights, and fit the formula for the discharge field strength as a function of specimen height. E exp3 = f 3( k Size effect check coefficient K c This refers to the ratio of the fitted or extrapolated discharge field strength of the test to the discharge field strength of the reference dataset when the test conditions and reference dataset have the same air pressure, the same mixing ratio, and different insulation specimen heights; the size effect verification requirement is 1- d c <K c <1+ d c , d c To allow for the size effect check margin, the consistency condition of the size effect check must be met.

[0032] To perform a ratio check, the mixing ratio of the perfluoroisobutyronitrile mixed insulating gas is adjusted. Steps S23-S24 are repeated to obtain the discharge voltage and discharge field strength under different mixing ratios, and a formula for the discharge field strength as a function of the mixing ratio is fitted. E exp2 = f 2( k Proportional verification factor K bThis refers to the ratio of the fitted or extrapolated value of the test discharge field strength to the discharge field strength of the reference dataset when the test conditions and the reference dataset have the same air pressure, the same insulating specimen height, but different mixing ratios; the ratio verification requirement is 1- d b <K b <1+ d b , d b To allow for a margin in proportional verification, the consistency condition of proportional verification must be met.

[0033] Therefore, this invention employs the aforementioned method for verifying the consistency of surface discharge field strength in a perfluoroisobutyronitrile (PFOS) mixed gas. This method effectively addresses the issues of poor data consistency and lack of systematic verification methods for surface discharge field strength in PFOS mixed insulating gases. Quantitative verification is achieved through pressure, size effect, and proportional three-dimensional coefficients, unifying test data under different operating conditions. Standardized test procedures reduce test errors, accurately obtain the true surface discharge field strength, and improve the safety and accuracy of surface insulation design. Verified data can be iteratively expanded to include a reference dataset. The method is simple to implement and adaptable to multiple scenarios.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for verifying the consistency of surface discharge field strength in a perfluoroisobutyronitrile mixed gas, characterized in that, Includes the following steps: S1. Construct a reference dataset of surface discharge field strength of perfluoroisobutyronitrile mixed insulating gas under different test conditions based on publicly available data. The test conditions include the mixing ratio, gas pressure, and height of the insulating specimen of the perfluoroisobutyronitrile mixed insulating gas. S2. Conduct surface discharge tests to obtain the surface discharge field strength of perfluoroisobutyronitrile mixed insulating gas under different insulation test heights and different gas pressures. S3, Introduce pressure verification coefficient K y Size effect check coefficient K c and proportional verification coefficient K b The discharge field strength test values ​​obtained in S2 are then checked for pressure, size effect, and proportion. If the corresponding check requirements are met, the discharge field strength test results of S2 are deemed to be consistent. If the check requirements are not met, S2 is repeated until the test results meet the check requirements. S4. The test results that meet the verification requirements are incorporated into the reference dataset of S1 as reference data for subsequent test data consistency verification.

2. The method for verifying the consistency of surface discharge field strength of perfluoroisobutyronitrile mixed gas according to claim 1, characterized in that, In S1, the surface discharge field strength of the perfluoroisobutyronitrile mixed insulating gas is the ratio of the discharge voltage of the cylindrical insulating sample to the height of the sample. E ref The perfluoroisobutyronitrile mixed insulating gas is formed by mixing perfluoroisobutyronitrile with one or two of the following gases: N2, CO2, and O2, in a preset ratio.

3. The method for verifying the consistency of surface discharge field strength of perfluoroisobutyronitrile mixed gas according to claim 2, characterized in that, In S2, the surface discharge test specifically includes the following: S21. Construct a surface discharge test model, which includes a high-voltage electrode, a grounding electrode, and a solid insulating test specimen placed between the two electrodes. The electrodes adopt a plate-to-plate structure to form a clear surface path. S22. Place the surface discharge test model in a sealed test container with controllable gas pressure, and fill it with a pre-proportioned perfluoroisobutyronitrile mixed insulating gas to the set pressure. S23. Apply a standard lightning impulse voltage and use the step-up / step-down method to obtain the surface discharge voltage. U d That is, the voltage at which the probability of surface flashover is 50%; S24. Based on the height of the insulation test specimen d Discharge voltage U d Calculate the surface discharge field strength E exp ; S25. Within a certain range, adjust the air pressure to different values, repeat steps S23-S24, obtain the discharge voltage and discharge field strength under different air pressures, and fit the formula for the change of discharge field strength with air pressure. E exp1 = f 1( p ); S26. Adjust the mixing ratio of the perfluoroisobutyronitrile mixed insulating gas, repeat steps S23-S24, obtain the discharge voltage and discharge field strength under different mixing ratios, and fit the formula for the change of discharge field strength with mixing ratio. E exp2 = f 2( k ); S27. Adjust the height of the insulating test specimen, repeat steps S23-S24, obtain the discharge voltage and discharge field strength at different specimen heights, and fit the formula for the change of discharge field strength with specimen height. E exp3 = f 3( k ).

4. The method for verifying the consistency of surface discharge field strength of perfluoroisobutyronitrile mixed gas according to claim 3, characterized in that, In S3, the pressure verification coefficient K y This refers to the ratio of the fitted or extrapolated value of the test discharge field strength to the discharge field strength of the reference dataset when the test conditions and the same insulating specimen height, the same mixing ratio, and different air pressures are the same; the pressure verification requirement is 1- δ y <K y <1+ δ y , δ y Allowable margin for stress verification; The size effect check coefficient K c , is the ratio of the fitted or extrapolated value of the test discharge field strength to the discharge field strength of the reference dataset when the test conditions and the reference dataset have the same air pressure, the same mixing ratio, and different insulation specimen heights. Size effect verification requirement is 1- δ c <K c <1+ δ c , δ c Check the allowable margin for size effect; The proportional verification coefficient K b , is the ratio of the fitted or extrapolated value of the test discharge field strength to the discharge field strength of the reference dataset when the test conditions and the reference dataset have the same air pressure, the same height of the insulating specimen, and different mixing ratios. The proportional verification requirement is 1- δ b <K b <1+ δ b , δ b This is for the allowable margin of proportional verification.

5. The method for verifying the consistency of surface discharge field strength of perfluoroisobutyronitrile mixed gas according to claim 4, characterized in that, In S3, the verification requirement is to meet any one of the verification conditions of pressure verification, size effect verification, and proportional verification.

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